1. Field of the Invention
The present invention relates to a thermoplastic resin composition which has good flowability and can impart a uniformly delustered surface and improved properties such as impact resistance to a molded article.
2. Description of the Related Art
A rubber-modified styrene base thermoplastic resin a typical example of which is an ABS resin (acrylonitrilediene rubber-styrene copolymer) has good mechanical properties such as impact resistance, stiffness, etc. and good appearance of the molded article. Therefore, the rubber-modified styrene base thermoplastic resin is used as a material of, for example, automobile parts, business machine parts and haberdasheries. In view of safety and matching with other parts or of achieving a mat type calm hand, low gloss delustered resin articles are desired for the automobile parts, particularly, the automobile interior parts.
To impart a delustered surface to a resin article, following measures have been proposed:
i) addition of an inorganic filler such as calcium carbonate, PA1 ii) addition of a rubbery polymer, PA1 iii) incorporation of an ethylenically unsaturated carboxylic acid in the styrene base thermoplastic resin by copolymerization, and PA1 iv) addition of a copolymer of an olefin having an epoxy group. PA1 (A) 40 to 99.8 parts by weight of a rubber-modified styrene base thermoplastic resin, PA1 (B) 0.1 to 20 parts by weight of a copolymer having an epoxy group but comprising no olefin, and PA1 (C) 0.1 to 50 parts by weight of a polymer having at least one functional group selected from the group consisting of a carboxyl group, an acid anhydride group, a hydroxyl group and a nitrogen-containing base group with the total amount of the rubber-modified styrene base thermoplastic resin (A), the copolymer (B) and the polymer (C) being 100 parts by weight and the content of the rubber in the composition being from 5 to 40% by weight based on the weight of the composition.
However, the addition of the inorganic filler considerably deteriorates the impact resistance which is one of the characteristics of the rubber-modified thermoplastic resin. The addition of the rubbery polymer generates defects such as flow marks on the surface of the molded article so that no uniformly delustered surface is obtained. The incorporation of the ethylenically unsaturated carboxylic acid gives uneven gloss on the surface of the molded article. In comparison with the above three measures, the addition of the polymer of the olefin having an epoxy group has good delustering effects and forms a uniformly delustered surface without defects. However, as the amount of the polymer added to the rubber-modified styrene base thermoplastic resin increases, the flowability and impact resistance, particularly notched impact resistance are decreased.